1. Technical Field
The present invention relates to a method and apparatus for cleaning operating components of a video player/recorder.
2. Background Art
In recent years, video player/recorders have become quite popular. Typically, there is a video head which either records or plays back the video portion of the playing tape, an audio head which performs the same functions for the sound portion of the tape, an erase head, and possibly other components which engage the tape. In the proper operation of the player/recorder, it is desirable that the surface portion of at least some (and desirably all) of these components which contact the tape be cleaned periodically. There are in the prior art cassette cleaners which have a cassette housing in which is mounted a cleaning ribbon. In operation, the cassette housing is placed into a playing receptacle of the player/recorder, and the start knob or button is moved to the "on" position so that guide members of the player/recorder engage the cleaning ribbon and bring it into engagement with at least the drum of the video head, and in some instances, the other operating components which would normally come into contact with the playing tape.
In some player/recorders, the drum in which the playing head is mounted rotates at a high rate of speed. In other player/recorders, the drum for the playing head remains stationary, while the playing head itself rotates at a high rate of speed along the circumference of the drum. During the normal mode of operation, the magnetic tape which is either being played or on which the recording is being made moves along its length at a controlled rate of speed adjacent the playing head. If the drum of the playing head is stationary, the relative movement between the magnetic tape and the drum is at a substantially lower level. On the other hand, if the drum is rotating at a high rate of speed (e.g. 1000 to 2000 revolutions per minute), the relative speed between the drum and the magnetic tape is rather high.
In general, the cassette cleaners have had the cleaning ribbon mounted in one of two ways. In one arrangement, the cleaning ribbon is moved out of the cassette housing into engagement with the drum of the cleaning head, and the cleaning ribbon does not move along its axial length. Thus, it is the rapid rotation of the drum of the cleaning head which accounts for the relative movement between the cleaning ribbon and the drum. In the second arrangement, the cleaning ribbon is mounted on spools within the cassette housing so that after it is moved out of the cassette housing into cleaning engagement with the drum (and possibly other components of the player/recorder), the cleaning ribbon moves along its axial length at substantially the same rate of speed as the magnetic tape in the normal mode of operation of the player/recorder. In either case, there is relative movement between the cleaning ribbon and the drum of the playing head.
One of the major problems in providing such cassette cleaners is the sensitivity of the operating components of the various player/recorders. For example, the cassettes for magnetic tapes generally have two spools which engage spindles of the player/recorder. During normal operations, the magnetic tape will be unwound from one spool and wound onto the other. If the spindles (or possibly other operating components of the player/recorder) sense a resistance to rotation greater than a certain level, this will generally activate a shutoff mechanism in the player/recorder. The reason for this is that the increased resistance indicates a problem, and the player/recorder shuts off to avoid damage to the magnetic tape or possibly damage to the player/recorder itself.
In addition, a number of player/recorders have other shutoff mechanisms. For example, there are the capstan and pinch roller which grip opposite sides of the tape, with the capstan being rotated under power so as to cause rotation of the pinch roller and move the magnetic tape along its length at a controlled rate. If for some reason the capstan is not causing the corresponding rotation of the pinch roller, so that the tape is not being moved, this might also trigger a shutoff mechanism.
Generally, the magnetic tape is made of a quite thin, rather flexible, low friction material. However, the cleaning ribbon of a cassette cleaner, in order to perform its cleaning function properly, has a somewhat different structure. First, it will generally be made of an absorbant material so that it can absorb a cleaning liquid. Second, since the cleaning is achieved by a wiping action against the drum, and possibly other components of the player/recorder, the friction of the cleaning ribbon moving relative to the drum may be somewhat greater than the friction of the conventional magnetic tape moving through the player/recorder and against the drum. Further, the cleaning ribbon is quite often made somewhat thicker than the conventional magnetic tape, so it would be more absorbant, with the result that if the cleaning ribbon is arranged so that it moves through the player/recorder along generally the same path as the magnetic tape, the greater stiffness of the cleaning ribbon (relative to the magnetic tape) might create greater resistance to the movement of the cleaning ribbon. Overall, these various operating characteristics of the cleaning ribbon sometimes create sufficient resistance to the operating components of the player/recorder so as to trigger an automatic shutoff mechanism of the player/recorder, thus prematurely stopping the cleaning action.
A further complicating factor is that quite commonly the action of the cleaning fluid increases the frictional force resulting from engagement of the wetted ribbon against the drum. Thus, there is a tendency for the cleaning ribbon to create an excessive resisting force to the rotation of the drum, thus prematurely triggering the shutoff mechanism of the player/recorder. There have been various attempts to lower the resistance created by the cleaning ribbon, such as modifying the material used, the thickness of the material, the material's absorbancy, etc. In some instances, such attempts to decrease the frictional resistance or other resistance have the effect of diminishing the cleaning effectiveness of the ribbon.